In his 1988 congressional testimony, climatologist James Hansen presented climate models that projected continual global warming, stating that the evidence was strong that the "greenhouse effect" was already here. Since that time he has voiced increasing concern about the risks of climatic tipping points that could bring catastrophic consequences to the planet.

Speaking of Hurricane Sandy, Hansen spoke of the warming in the Atlantic driving cyclonic storms, which, unlike a hurricane, stretch for thousands of miles. "If you get a hurricane embedded in one of those, that's when you get a higher dose. That's what we had with Sandy." He went on to say, "The dice are now loaded. Not only do you get more unusually warm seasons, but those that are most extreme are much more frequent than they used to be." Is there a human fingerprint on Sandy? "You can't blame a single event and connect that in a simple way to global warming, but the frequency and extremity of those events you can connect to global warming in a very straightforward way."

Hansen advocates putting pressure on politicians. As one who has himself been arrested for civil disobedience, he said, "I really object to politicians and others who say that scientists should just stick to the narrow science and not look at the whole problem, because you do have to connect the dots. Scientists are actually trained to be objective and to understand complex problems. This is a complex problem."

And the solution? The incentive to change is carbon tax, collecting from fossil fuel companies at the source-at the mine or the port of entry-and distributing it, 100%, to the public, to every person in the country, he says. "As long as fossil fuels are the cheapest energy, then people will keep burning them. And they're cheapest because they are not only subsidized, but they don't pay their cost to society." He spoke of the health problems caused by air and water pollution, and the cost of extreme weather-"$50B from Sandy in New York, $50B in New Jersey. The drought last summer took half a point off GDP growth. The public pays the cost." With a rising price on fossil fuels, the marketplace will make the decisions. What about the increasing use of fossil fuels in other countries, such as China and India? Put a carbon tax on their products when they arrive at the border, he said, saying it would be an enormous incentive for them to reduce their carbon use at home.

Looking toward the future, Hansen spoke of the need to help young people better understand nature. With that goal, he is currently writing a book with his fourteen-year-old granddaughter, Sophie.

Climatologist James Hansen explains why government subsidies play a large role in propping up the fossil fuel industry. "Letting the marketplace decide which industries are best for the environment is libertarian, populist, and democratic," Hansen argues.